Recently, with the advancement of craft techniques and the improvement of living standards, people who intend to buy a new product consider not only the price and durability of the product, but also whether the product is convenient and safe to use. Such a change in market trends has driven manufacturers and designers in all fields to develop new and better products on a regular basis so as to meet consumers' needs. Take the folding knife commonly used in outdoor recreational activities for example. The conventional folding knife is provided with a resilient locking arm in the handle. When the blade of the folding knife is received in the handle, the resilient locking arm is movably pressed against a lateral side of the blade. Once the blade is rotated out of the handle completely, the end of the resilient locking arm that slants toward the inside of the blade is movably pressed against one end of the blade. Thus, the resilient locking arm holds the blade in place and increases the stability of the folding knife in use. However, as the resilient locking arm is installed in the handle in a movable manner, the aforesaid end of the resilient locking arm may deform and therefore fail to press against the blade when the blade is subjected to an excessively large force. Should it happen, the user is very likely to be accidentally cut by the blade. To solve this problem, improved folding knife structures that feature enhanced stability in use were proposed.
For example, referring to FIG. 1 for a folding knife disclosed in U.S. Pat. No. 7,437,822B2, the folding knife 1 includes a blade 11, a handle 13, and a pushing device 15. The handle 13 includes a first panel 131, a second panel 132, and a third panel 133. The panels 131, 132, 133 are connected together by a pivot 110 passing through the panels at a position adjacent to one end thereof. The pivot 110 also extends through the blade 11 such that a portion of the blade 11 that is adjacent to one end thereof is fixed in position between the first panel 131 and the second panel 132. The second panel 132 is provided with a resilient locking arm 132a which has a first end fixed to the second panel 132 and a second end extending slantingly toward the first panel 131. Hence, while the blade 11 is being rotated out of the handle 13 from a first side thereof, a lateral surface of the resilient locking arm 132a is pressed against a lateral surface of the blade 11, and once the blade 11 is rotated out of the handle 13 completely, the second end of the resilient locking arm 132a is pressed against the aforesaid end of the blade 11 to prevent the blade 11 from rotating back toward the handle 13. The third panel 133 is concavely provided with a receiving groove 133a. A post 133b is provided in the receiving groove 133a and is adjacent to a first end thereof. The pushing device 15 consists of a pushing element 151 and a restoring spring 152. The pushing element 151 corresponds in configuration to a portion of the receiving groove 133a that is adjacent to a second end thereof. Thus, with the pivot 110 passing through the middle portion of the pushing element 151, the pushing element 151 not only can be received in a second end of the receiving groove 133a, but also can be rotated therein about the pivot 110. The pushing element 151 further has a projection 151a and a pushing portion 151b, wherein the projection 151a projects toward the second panel 132, and the pushing portion 151b extends outward of the handle 13. The restoring spring 152 has a first end that corresponds in configuration to and is positioned in the first end of the receiving groove 133a. The middle portion of the restoring spring 152 is wound around the periphery of the post 133b. A second end of the restoring spring 152 extends toward the second end of the receiving groove 133a and is pressed against the projection 151a of the pushing element 151 such that the projection 151a is biased toward a second side of the handle 13 and can be moved to a position below the resilient locking arm 132a. Therefore, once the blade 11 is rotated out of the handle 13 completely, and the second end of the resilient locking arm 132a is pressed against the aforesaid end of the blade 11, the projection 151a is pressed against the other lateral surface of the resilient locking arm 132a to prevent the resilient locking arm 132a from being pressed toward the third panel 133, thereby ensuring the stability of the blade 11 during use. When the folding knife 1 is no longer in use, the blade 11 can be folded into the handle 13 as follows. First, the pushing portion 151b is pushed to rotate the projection 151a toward the first side of the handle 13 from below the resilient locking arm 132a. Then, the resilient locking arm 132a is pressed to release the blade 11 from the pressing of the resilient locking arm 132a, so that the blade 11 can be rotated into the handle 13. In the conventional folding knife design described above, the projection 151a of the pushing element 151 is configured to provide increased support for the resilient locking arm 132a, and yet the folding knife 1 still has the following drawbacks:
(1) A complicated overall structure and an elaborate assembly process: During assembly of the folding knife 1, the pushing element 151 must be mounted around the pivot 110 before the first end of the restoring spring 152 is positioned in the first end of the receiving groove 133a. Afterward, the restoring spring 152 must be wound around the post 133b such that the second end of the restoring spring 152 is pressed against the projection 151a. This assembly process is far more complicated than that of the conventional folding knife and demands absolute concentration and patience from the assembly operator. In consequence, the folding knife 1 is very likely to be manufactured at low efficiency and high cost.
(2) Insecureness of the pushing device 15: As the restoring spring 152 is positioned in the receiving groove 133a by winding around the post 133b, the second end of the restoring spring 152 must be placed precisely against the projection 151a in order to bias the pushing element 151. However, when the folding knife 1 is subjected to an external impact, the restoring spring 152 tends to loosen or be shifted in position such that the second end thereof no longer presses against the projection 151a, or that the pushing device 15 becomes less responsive to the user's operation. Since durability has always been an important feature expected of folding knives, the aforesaid drawback of the folding knife 1 is highly undesirable.
To sum up, although the projection 151a of the pushing element 151 in the folding knife 1 serves to enhance the structural strength of the resilient locking arm 132a, the overall structure and the assembly procedure of the folding knife 1 are prohibitively complicated. Moreover, manufacture efficiency and product durability may be compromised when the pushing device 15 is impacted and loosened; in other words, the folding knife 1 does not provide a sound solution to improving the instability of the conventional folding knife during use. Therefore, the issue to be addressed by the present invention is to design a folding knife with a resilient locking arm, wherein the resilient locking arm not only features high structural strength but also ensures durability of the folding knife and can be easily installed so as to lower production costs effectively.